Producers of still pictures and motion video programs use a variety of special effects to produce a final product. A graphics editor performs the task of adding special effects to still pictures and to motion video segments using a graphics workstation.
Color changing is a special effect that involves changing the color of certain pixels within one or more video image frames. One application of color changing involves modifying the color of an object to make it more or less noticeable in the video image frame. Another application of color changing is to repair a damaged portion of the video image frame. A third application of color changing is to add color to a video image frame to generate the appearance of one or more new objects in the video image frame.
To achieve a color change effect, the graphics editor, using a mouse, graphics tablet or similar input device, manually circumscribes an area of a video image frame that is to receive the color change effect using the graphics workstation. Then, the graphics editor changes the color of each pixel within the circumscribed area to a specified destination color.
Since every pixel within the circumscribed area is changed to the new destination color, the graphics editor must circumscribe the intended color change area with precision. If the graphics editor does a poor job of circumscribing the area, some pixels that were not intended to be changed may be changed, and some pixels intended to be changed may be left unchanged.
Generally, the graphics editor's ability to circumscribe an object in a video image frame is limited. One way for the graphics editor to circumscribe the object is by controlling a cursor on the graphics workstation by manually moving a mouse. In particular, the graphics editor attempts to exactly trace the border around the object with the cursor. Such work requires good hand-eye coordination and is typically painstaking.
Producing color change effects using the above-described technique has additional drawbacks. In particular, setting each pixel of an object to be a destination color generally makes the object look flat and two-dimensional rather than three-dimensional which is often preferred. Additionally, it is not practical for a graphics editor to perform this process on frames of motion video footage that may include a sequence of hundreds or even thousands of individual frames. Furthermore, conventional color correction algorithms performed on computers are complex and require substantial computer power.